The present invention is generally related to steering means for marine propulsion systems, and, more particularly, the present invention is related to an integral-piece gimbal ring and steering assembly for a stern drive propulsion system.
Although marine propulsion systems, such as stern drives, provide versatile and proficient means of propulsion to pleasure boats, etc., typical stern drive systems have presented some challenges to boat manufacturers and servicing personnel, such as maintenance and/or assemblage complexity of their steering means to a gimbal ring.
FIG. 1 illustrates a prior art gimbal ring 10 that allows for providing superior boat control by steering about a generally vertical steering axis, and trimming about a generally horizontal axis. Important to the steering function is an upper pivot pin 12 that in cooperation with a cross bolt 14 allows for securing a steering arm 16 to the gimbal ring. Notwithstanding that the parts for providing the steering function may be machined to achieve a tight pivoting joint, due to the effects of various loads, such as may be generated from steering, vibration, wave impact, hydrodynamic side loads, underwater impact, etc., such joint may require frequent servicing to maintain the tight joint.
Further being that pivot pin 12 and gimbal ring 10 comprise separate pieces generally made of different metals or metal alloys, such multi-piece construction may result in cathodic corrosion between one another. For example, in one common arrangement, pivot pin 12 may be made of hardened iron and gimbal ring 10 may be made of aluminum. Once again, frequent servicing may be needed to control corrosion in the joint.
As further shown in FIG. 1, such arrangement generally requires a relatively large number of parts, including square-shaped joint surfaces and mating splines subject to high stress which may become deformed between the relatively soft aluminum gimbal and the hardened pivot pin.
Thus, it would be desirable to provide an integral-piece gimbal ring and steering assembly that allows for overcoming the above-described difficulties.
Generally speaking, the present invention fulfills the foregoing needs by providing in one embodiment a marine propulsion system made up of a gimbal housing affixed through the rear of a boat transom and a gimbal ring pivotally connected to the gimbal housing. The system is further made up of a steering assembly configured to provide pivotal movement of the gimbal ring relative to the gimbal housing about a steering axis. The gimbal ring and the steering assembly comprise an integral-piece assembly.
The present invention may further fulfill the foregoing needs by providing in another embodiment a method of assembling a marine propulsion system. The method allows for affixing a gimbal housing through the rear of a boat transom. The method further allows for pivotally connecting a gimbal ring to the gimbal housing, and for forming, e.g., casting or welding, or both, an integral-piece gimbal ring and steering assembly configured to provide pivotal movement of the gimbal ring relative to the gimbal housing about a steering axis.